EIF2AK3 and Alzheimer disease: Serum and brain TMAO: higher in 3xTg-AD and db/db mice at 8 months vs. controls, further increased in 3xTg-AD mice at 18 months vs. controls Hippocampal slices: reduced LTP and impaired synaptic transmission through induction of the PERK-EIF2α-endoplasmic reticulum stress signaling axis in TMAO incubated slices vs. controls